logoassistant-ui

Generative UI

Create custom UI components for AI tool calls, providing visual feedback and interactive experiences when tools are executed.

Sample Tool UI
Ask 'what is the weather in Tokyo?'

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Overview

Tool UIs in assistant-ui allow you to create custom interfaces that appear when AI tools are called. These generative UI components enhance the user experience by:

  • Visualizing tool execution with loading states and progress indicators
  • Displaying results in rich, formatted layouts
  • Enabling user interaction through forms and controls
  • Providing error feedback with helpful recovery options

This guide demonstrates building tool UIs with the Vercel AI SDK.

Creating Tool UIs

There are two main approaches to creating tool UIs in assistant-ui:

1. Client-Defined Tools (makeAssistantTool)

If you're creating tools on the client side, use makeAssistantTool to register them with the assistant context. Then create a UI component with makeAssistantToolUI:

import { makeAssistantTool, tool } from "@assistant-ui/react";
import { z } from "zod";

// Define the tool
const weatherTool = tool({
  description: "Get current weather for a location",
  parameters: z.object({
    location: z.string(),
    unit: z.enum(["celsius", "fahrenheit"]),
  }),
  execute: async ({ location, unit }) => {
    const weather = await fetchWeatherAPI(location, unit);
    return weather;
  }
});

// Register the tool
const WeatherTool = makeAssistantTool(weatherTool);

// Create the UI
const WeatherToolUI = makeAssistantToolUI<
  { location: string; unit: "celsius" | "fahrenheit" },
  { temperature: number; description: string }
>({
  toolName: "getWeather",
  render: ({ args, result, status }) => {
    if (status.type === "running") {
      return <div>Checking weather in {args.location}...</div>;
    }

    return (
      <div className="weather-card">
        <h3>{args.location}</h3>
        <p>
          {result.temperature}°{args.unit === "celsius" ? "C" : "F"}
        </p>
        <p>{result.description}</p>
      </div>
    );
  },
});

Tools defined with makeAssistantTool can be passed to your backend using the frontendTools utility

Learn more about creating tools in the Tools Guide.

2. UI-Only for Existing Tools (makeAssistantToolUI)

If your tool is defined elsewhere (e.g., in your backend API, MCP server, or LangGraph), use makeAssistantToolUI to create just the UI component:

import { makeAssistantToolUI } from "@assistant-ui/react";

const WeatherToolUI = makeAssistantToolUI<
  { location: string; unit: "celsius" | "fahrenheit" },
  { temperature: number; description: string }
>({
  toolName: "getWeather", // Must match the backend tool name
  render: ({ args, result, status }) => {
    // UI rendering logic only
  },
});

Quick Start Example

This example shows how to implement the UI-only approach using makeAssistantToolUI:

Create a Tool UI Component

import { makeAssistantToolUI } from "@assistant-ui/react";
import { z } from "zod";

type WeatherArgs = {
  location: string;
  unit: "celsius" | "fahrenheit";
};

type WeatherResult = {
  temperature: number;
  description: string;
  humidity: number;
  windSpeed: number;
};

const WeatherToolUI = makeAssistantToolUI<WeatherArgs, WeatherResult>({
  toolName: "getWeather",
  render: ({ args, status, result }) => {
    if (status.type === "running") {
      return (
        <div className="flex items-center gap-2">
          <Spinner />
          <span>Checking weather in {args.location}...</span>
        </div>
      );
    }

    if (status.type === "incomplete" && status.reason === "error") {
      return (
        <div className="text-red-500">
          Failed to get weather for {args.location}
        </div>
      );
    }

    return (
      <div className="weather-card rounded-lg bg-blue-50 p-4">
        <h3 className="text-lg font-bold">{args.location}</h3>
        <div className="mt-2 grid grid-cols-2 gap-4">
          <div>
            <p className="text-2xl">
              {result.temperature}°{args.unit === "celsius" ? "C" : "F"}
            </p>
            <p className="text-gray-600">{result.description}</p>
          </div>
          <div className="text-sm">
            <p>Humidity: {result.humidity}%</p>
            <p>Wind: {result.windSpeed} km/h</p>
          </div>
        </div>
      </div>
    );
  },
});

Register the Tool UI

Place the component inside your AssistantRuntimeProvider:

function App() {
  return (
    <AssistantRuntimeProvider runtime={runtime}>
      <Thread />
      <WeatherToolUI />
    </AssistantRuntimeProvider>
  );
}

Define the Backend Tool (Vercel AI SDK)

When using the Vercel AI SDK, define the corresponding tool in your API route:

/app/api/chat/route.ts
import { streamText, tool } from "ai";
import { z } from "zod";

export async function POST(req: Request) {
  const { messages } = await req.json();

  const result = streamText({
    model: openai("gpt-4o"),
    messages,
    tools: {
      getWeather: tool({
        description: "Get current weather for a location",
        parameters: z.object({
          location: z.string(),
          unit: z.enum(["celsius", "fahrenheit"]),
        }),
        execute: async ({ location, unit }) => {
          const weather = await fetchWeatherAPI(location);
          return {
            temperature: weather.temp,
            description: weather.condition,
            humidity: weather.humidity,
            windSpeed: weather.wind,
          };
        },
      }),
    },
  });

  return result.toDataStreamResponse();
}

Tool UI Patterns

Component Pattern

Create standalone tool UI components:

export const WebSearchToolUI = makeAssistantToolUI<
  { query: string },
  { results: SearchResult[] }
>({
  toolName: "webSearch",
  render: ({ args, status, result }) => {
    return (
      <div className="search-container">
        <div className="mb-3 flex items-center gap-2">
          <SearchIcon />
          <span>Search results for: "{args.query}"</span>
        </div>

        {status.type === "running" && <LoadingSpinner />}

        {result && (
          <div className="space-y-2">
            {result.results.map((item, index) => (
              <div key={index} className="rounded border p-3">
                <a href={item.url} className="font-medium text-blue-600">
                  {item.title}
                </a>
                <p className="text-sm text-gray-600">{item.snippet}</p>
              </div>
            ))}
          </div>
        )}
      </div>
    );
  },
});

Hook Pattern

Use hooks for dynamic tool UI registration:

When you assign your makeAssistantToolUI({...}) call to a constant starting with use…, you can call it directly as a hook inside your component. This pattern lets you access local props or state when rendering the tool UI.

import { useAssistantToolUI } from "@assistant-ui/react";

function DynamicToolUI() {
  const [theme, setTheme] = useState("light");

  useAssistantToolUI({
    toolName: "analyzeData",
    render: ({ args, result, status }) => {
      // Hook allows access to component state
      return (
        <DataVisualization
          data={result}
          theme={theme}
          loading={status.type === "running"}
        />
      );
    },
  });

  return null;
}

Inline Pattern

For tools that need access to parent component props:

Why useInlineRender? By default, a tool UI's render function is static. Use useInlineRender when your UI needs access to dynamic component props (for example, to pass in an id or other contextual data).

import { useAssistantToolUI, useInlineRender } from "@assistant-ui/react";

function ProductPage({ productId, productName }) {
  useAssistantToolUI({
    toolName: "checkInventory",
    render: useInlineRender(({ args, result }) => {
      // Access parent component props
      return (
        <div className="inventory-status">
          <h4>{productName} Inventory</h4>
          <p>
            Stock for {productId}: {result.quantity} units
          </p>
          <p>Location: {result.warehouse}</p>
        </div>
      );
    }),
  });

  return <div>Product details...</div>;
}

Interactive Tool UIs

User Input Collection

Create tools that collect user input during execution:

Pro tip: Call addResult(...) exactly once to complete the tool call. After it's invoked, the assistant will resume the conversation with your provided data.

const DatePickerToolUI = makeAssistantToolUI<
  { prompt: string },
  { date: string }
>({
  toolName: "selectDate",
  render: ({ args, result, addResult }) => {
    if (result) {
      return (
        <div className="rounded bg-green-50 p-3">
          ✅ Selected date: {new Date(result.date).toLocaleDateString()}
        </div>
      );
    }

    return (
      <div className="rounded border p-4">
        <p className="mb-3">{args.prompt}</p>
        <DatePicker
          onChange={(date) => {
            addResult({ date: date.toISOString() });
          }}
        />
      </div>
    );
  },
});

Multi-Step Interactions

Build complex workflows with multiple user interactions:

const ApprovalToolUI = makeAssistantToolUI<
  { action: string; details: any },
  { approved: boolean; reason?: string }
>({
  toolName: "requestApproval",
  render: ({ args, result, addResult }) => {
    const [reason, setReason] = useState("");

    if (result) {
      return (
        <div className={result.approved ? "text-green-600" : "text-red-600"}>
          {result.approved ? "✅ Approved" : `❌ Rejected: ${result.reason}`}
        </div>
      );
    }

    return (
      <div className="rounded border-2 border-yellow-400 p-4">
        <h4 className="font-bold">Approval Required</h4>
        <p className="my-2">{args.action}</p>
        <pre className="rounded bg-gray-100 p-2 text-sm">
          {JSON.stringify(args.details, null, 2)}
        </pre>

        <div className="mt-4 flex gap-2">
          <button
            onClick={() => addResult({ approved: true })}
            className="rounded bg-green-500 px-4 py-2 text-white"
          >
            Approve
          </button>
          <button
            onClick={() => addResult({ approved: false, reason })}
            className="rounded bg-red-500 px-4 py-2 text-white"
          >
            Reject
          </button>
          <input
            type="text"
            placeholder="Rejection reason..."
            value={reason}
            onChange={(e) => setReason(e.target.value)}
            className="flex-1 rounded border px-2"
          />
        </div>
      </div>
    );
  },
});

Advanced Features

Tool Status Handling

The status prop provides detailed execution state:

render: ({ status, args }) => {
  switch (status.type) {
    case "running":
      return <LoadingState />;

    case "requires-action":
      return <UserInputRequired reason={status.reason} />;

    case "incomplete":
      if (status.reason === "cancelled") {
        return <div>Operation cancelled</div>;
      }
      if (status.reason === "error") {
        return <ErrorDisplay error={status.error} />;
      }
      return <div>Failed: {status.reason}</div>;

    case "complete":
      return <SuccessDisplay />;
  }
};

Field-Level Validation

Use useToolArgsFieldStatus to show validation states:

import { useToolArgsFieldStatus } from "@assistant-ui/react";

const FormToolUI = makeAssistantToolUI({
  toolName: "submitForm",
  render: ({ args }) => {
    const emailStatus = useToolArgsFieldStatus("email");
    const phoneStatus = useToolArgsFieldStatus("phone");

    return (
      <form className="space-y-4">
        <div>
          <input
            type="email"
            value={args.email}
            className={emailStatus.type === "running" ? "loading" : ""}
            disabled
          />
          {emailStatus.type === "incomplete" && (
            <span className="text-red-500">Invalid email</span>
          )}
        </div>

        <div>
          <input
            type="tel"
            value={args.phone}
            className={phoneStatus.type === "running" ? "loading" : ""}
            disabled
          />
        </div>
      </form>
    );
  },
});

Partial Results & Streaming

Display results as they stream in:

const AnalysisToolUI = makeAssistantToolUI<
  { data: string },
  { progress: number; insights: string[] }
>({
  toolName: "analyzeData",
  render: ({ result, status }) => {
    const progress = result?.progress || 0;
    const insights = result?.insights || [];

    return (
      <div className="analysis-container">
        {status.type === "running" && (
          <div className="mb-4">
            <div className="mb-1 flex justify-between">
              <span>Analyzing...</span>
              <span>{progress}%</span>
            </div>
            <div className="w-full rounded bg-gray-200">
              <div
                className="h-2 rounded bg-blue-500"
                style={{ width: `${progress}%` }}
              />
            </div>
          </div>
        )}

        <div className="space-y-2">
          {insights.map((insight, i) => (
            <div key={i} className="rounded bg-gray-50 p-2">
              {insight}
            </div>
          ))}
        </div>
      </div>
    );
  },
});

Custom Tool Fallback

Provide a custom UI for tools without specific UIs:

<Thread
  components={{
    ToolFallback: ({ toolName, args, result }) => (
      <div className="tool-fallback rounded bg-gray-100 p-3">
        <code className="text-sm">
          {toolName}({JSON.stringify(args)})
        </code>
        {result && (
          <pre className="mt-2 text-xs">{JSON.stringify(result, null, 2)}</pre>
        )}
      </div>
    ),
  }}
/>

Execution Context

Generative UI components have access to execution context through props:

type ToolUIRenderProps<TArgs, TResult> = {
  // Tool arguments
  args: TArgs;
  argsText: string; // JSON stringified args

  // Execution status
  status: ToolCallContentPartStatus;
  isError?: boolean;

  // Tool result (may be partial during streaming)
  result?: TResult;

  // Tool metadata
  toolName: string;
  toolCallId: string;

  // Interactive callback
  addResult: (result: TResult) => void;

  // Optional artifact data
  artifact?: unknown;
};

Best Practices

1. Handle All Status States

Always handle loading, error, and success states:

render: ({ status, result, args }) => {
  if (status.type === "running") return <Skeleton />;
  if (status.type === "incomplete") return <ErrorState />;
  if (!result) return null;
  return <ResultDisplay result={result} />;
};

2. Provide Visual Feedback

Use animations and transitions for better UX:

<div
  className={cn(
    "transition-all duration-300",
    status.type === "running" && "opacity-50",
    status.type === "complete" && "opacity-100",
  )}
>
  {/* Tool UI content */}
</div>

3. Make UIs Accessible

Ensure keyboard navigation and screen reader support:

<button
  onClick={() => addResult(value)}
  aria-label="Confirm selection"
  className="focus:outline-none focus:ring-2"
>
  Confirm
</button>

4. Optimize Performance

Use useInlineRender to prevent unnecessary re-renders:

useAssistantToolUI({
  toolName: "heavyComputation",
  render: useInlineRender(({ result }) => {
    // Expensive rendering logic
    return <ComplexVisualization data={result} />;
  }),
});

Generative UI components are only displayed in the chat interface. The actual tool execution happens on the backend. This separation allows you to create rich, interactive experiences while keeping sensitive logic secure on the server.

  • Tools Guide - Learn how to create and use tools with AI models
  • Tool Fallback - Default UI for tools without custom components
  • API Reference - Detailed type definitions and component APIs

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